This invention relates to improvements in molded switch heads of the type shown in U.S. Pat. No. 2,820,123 issued to L. W. Higgins, R. S. Davis, and J. A. Herrmann.
Switches of the above noted type, in essence, provide first and second stationary contacts which are engaged and disengaged by a movable contact element or slug. The contact slug is positioned in the switch head and the switch head is further constructed so as to move an insulating barrier between the stationary contacts as the contact slug is moved to a disengaged position. The head is further constructed so as to completely surround the area of contact and engagement with an insulating means. Hence, as the switch head is moved to a disengaged contact position, arcing between the stationary contacts is decreased, first because of the interposition of the insulating barrier and secondly, because the amount of oxygen or ionizable gas present is restricted in view of the insulated enclosure around the contact area.
In the past, it has been the practice to attach an operating clamp to the top of the insulating material of the switch head. The operating clamp provides a means whereby the switch head is moved between the engaged and disengaged positions. The novel switch head disclosed in U.S. Pat. No. 2,820,123 comprises, in part, first and second insulating head sections which telescope together in a horizontal direction. These head sections are held together in an operating clamp which is formed of a spring steel material. It has been found that for short circuit currents of 10,000 amps or less, the head segments can be held together only by the clamp. However, in circuits having possible short circuit currents over 10,000 amps, it is necessary to cement the two head segments together to provide adequate protection when a short occurs. If the head sections are not cemented together in the presence of short circuit currents of over 10,000 amps, it is possible that the head segments will separate.
The present invention provides a solution to the expensive manufacturing step of cementing head segments together, as well as providing an alternative to the expensively formed spring operating clamp.